16. Plant and Animal Hormones

I. Choose the Correct Answer.

1. Gibberellins cause _____.

(a) Shortening of genetically tall plants
(b) Elongation of dwarf plants
(c) Promotion of rooting
(d) Yellowing of young leaves.

2. The hormone which has positive effect on apical dominance is:

(a) Cytokinin               (b) Auxin
(c) Gibberellin             (d) Ethylene

3. Which one of the following hormones is naturally not found in plants?

(a) 2, 4 – D                 (b) GA3
(c) Gibberellin             (d) IAA.

4. Avena coleoptile test was conducted by:

(a) Darwin                   (b) N. Smit
(c) Paal                        (d) F.W. Went

5. To increase the sugar production in sugarcanes they are sprayed with _____.

(a) Auxin                     (b) Cytokinin
(c) Gibberellins           (d) Ethylene.

6. LH is secreted by:

(a) Adrenal gland
(b) Thyroid gland
(c) Anterior pituitary
(d) Hypothalamus

7. Identify the exocrine gland _____.

(a) Pituitary gland
(b) Adrenal gland
(c) Salivary gland
(d) Thyroid gland.

8. Which organ acts as both exocrine gland as well as endocrine gland?

(a) Pancreas               (b) Kidney
(c) Liver                      (d) Lungs

9. Which one is referred to as “Master Gland”?

(a) Pineal gland
(b) Pituitary gland
(c) Thyroid gland
(d) Adrenal gland.

II. Fill in the blanks.

1. Auxin causes cell elongation, apical dominance and prevents abscission.

2. Ethylene is a gaseous hormone involved in abscission of organs and acceleration of fruit ripening.

3. Abscisic acid causes stomatal closure.

4. Gibberellins induce stem elongation in Corn and Pea plants.

5. The hormone which has a negative effect on apical dominance is Cytokinin.

6. Calcium metabolism of the body is controlled by Parathormone.

7. In the Islets of Langerhans, beta cells secrete Insulin.

8. The growth and functions of the thyroid gland are controlled by Hormone T3 and T4

9. Decreased secretion of thyroid hormones in the children leads to Cretinism.

III. Match the following.

 (a) Match the Column I with Columns II and III.

Column I

Column II

Column III

Auxin

Coleoptile tip

Apical dominance

Ethylene

Fruits

Ripening

Abscisic acid

Chloroplast

Abscission

Cytokinin

Coconut milk

Cell division

Gibberellins

Gibberella fujikuroi

Intermodal elongation

(b) Match the following hormones with their deficiency states.

Hormones

Disorders

1. Thyroxine

(c) Simple goitre

2. Insulin

(e) Diabetes mellitus

3. Parathormone

(b) Tetany

4. Growth hormone

(a) Acromegaly

5. ADH

(d) Diabetes insipidus

IV. State whether True or false, If false write the correct statement.

1. A plant hormone concerned with stimulation of cell division and promotion of nutrient mobilization is cytokinin.
  Answer:         True.

2. Gibberellins cause parthenocarpy in tomato.
  Answer:         True.

3. Ethylene retards senescence of leaves, flowers and fruits.
  Answer:         False.
Correct Statement: Ethylene hastens the senescence of leaves, flowers and fruits.

4. Exophthalmic goitre is due to the over secretion of thyroxine.
  Answer:         True.

5. The pituitary gland is divided into four lobes.
  Answer:         False.
Correct Statement: The Pituitary gland is composed of two lobes and performs different functions.

6. Estrogen is secreted by corpus luteum.
  Answer:         False.
Correct Statement: Estrogen is produced by the Graafian follicles of the ovary.

V. Assertion and Reasoning Questions

Direction: In each of the following questions a statement of assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Mark the correct statement as,
(a) If both A and R are true and R is the correct explanation of A
(b) If both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) Both A and R are false.

1. Assertion(A): Application of cytokinin to marketed vegetables can keep them fresh for several days.
Reason(R): Cytokinins delay senescence of leaves and other organs by mobilisation of nutrients.
Answer:
(d) Both A and R are false.

2. Assertion (A): Pituitary gland is referred to as “Master gland”.
Reason (R): It controls the functioning of other endocrine glands.
Answer:
(a) If both A and R are true and R is the correct explanation of A.

3. Assertion (A): Diabetes mellitus increases blood sugar levels.
Reason (R): Insulin decreases blood sugar levels.
Answer:
(a) If both A and R are true and R is the correct explanation of A.

VI. Answer in a word or sentence.

1. Which hormone promotes the production of male flowers in Cucurbits?

Gibberellins promote the production of male flowers in Cucurbits.

2. Write the name of synthetic auxin.

2, 4 Dichloro phenoxy Acetic Acid is the synthetic hormone.

3. Which hormone induces parthenocarpy in tomatoes?

Gibberellins are efficient in the formation of seedless fruit, inducing parthenocarpy in tomatoes.

4. What is the hormone responsible for the secretion of milk in female after child birth?

Prolactin stimulates the secretion of milk in female after child birth.

5. Name the hormones which regulate water and mineral metabolism in man.

Antidiuretic or vasopressin hormone regulates water and mineral metabolism in man.

6. Which hormone is secreted during emergency situation in man?

Adrenaline and Noradrenaline is secreted during emergency situation in man.

7. Which gland secretes digestive enzymes and hormones?

The pancreas is exocrine and endocrine in nature. The exocrine pancreas secretes pancreatic juice which plays a role in digestion. The endocrine portion (Islets of Langerhans) secrete hormones.

8. Name the endocrine glands associated with kidneys.

Adrenal gland is associated with kidneys.

VII. Short Answer Questions.

1. What are synthetic auxins? Give examples.

Artificially synthesized auxins, which have the properties like auxins are called as synthetic auxins, eg. 2, 4-D (2, 4-Dichlorophenoxy Acetic acid, Indole-3-Propionic Acid, alpha – Naphthalene Acetic Acid (NAA), 2, 4, 5-T (2, 4, 5-Trichlorophenoxy Acetic acid) are some of the synthetic auxins.

2. What is bolting? How can it be induced artificially?

Rosette plant (genetic dwarfism) plant exhibit excessive intermodal growth when they are treated with gibberellins. This sudden elongation of a stem followed by flowering is called bolting.

3. Bring out any two physiological activities of abscisic acid.

·         During water stress and drought conditions, Abscisic acid causes stomatal closure.

·         ABA induces bud dormancy towards the approach of winter in trees like birch.

4. What will you do to prevent leaf fall and fruit drop in plants? Support your answer with reason.

Artificially synthesized auxin to be sprayed to prevent leaf fall and fruit drop as Auxin prevent the formation of abscission layer.

5. What are chemical messengers?

A chemical messenger is any compound that serves to transmit a message. A chemical messenger refers to hormones.

6. Write the differences between endocrine and exocrine gland.

The exocrine gland secretes juices, which plays a role in digestion. An endocrine portion is made up of endocrine glands, which secrete hormones. The pancreas is exocrine and endocrine in nature.

7. What is the role of parathormone?

Parathormone regulates calcium and phosphorous metabolism in the body. They act on bone, kidney and intestine to maintain blood calcium levels.

8. What are the hormones secreted by the posterior lobe of the pituitary gland? Mention the tissues on which they exert their effect.

·         Vasopressin or Antidiuretic hormone.

·         Oxytocin is the two hormones of the posterior lobe of the pituitary gland.

In kidney tubules, the vasopressin hormone increases the reabsorption of water. It reduces the loss of water through urine.
Oxytocin helps in the contraction of the smooth muscles of the uterus at the time of childbirth and ” milk ejection from the mammary gland after childbirth.

9. Why are thyroid hormones refered as personality hormone?

Thyroid hormones are essential for normal, physical, mental and personality development. So, it is called as personality hormone.

10. Which hormone requires iodine for its formation? What will happen if the intake of iodine in our diet is low?

The hormones secreted by the thyroid gland are:

  • Triiodothyronine (T3)1
  • Tetraiodothyronine or Thyroxin (T4), which need an amino acid tyrosine and Iodine for its formation.

If the intake of Iodine in our diet is low or due to the inadequate supply of iodine in our diet leads to the enlargement of the thyroid gland, which protrudes, as swelling in the neck and is called as goitre.

VIII. Long Answer Questions

1. (a) Name the gaseous plant hormone. Describe its three different actions in plants.

Ethylene is a gaseous plant hormone.

  1. Ethylene promotes the ripening of fruits. Eg: Tomato, Apple, Mango, Banana, etc.
  2. Ethylene inhibits the elongation of stem and root in dicots.
  3. Ethylene hastens the senescence of leaves and flowers.

(b) Which hormone is known as a stress hormone in plants? Why?
Answer:
Abscisic acid increases the tolerance of plants to various kinds of stress. So, it is also called a stress hormone. It is found in the chloroplast of plants.

2. Describe an experiment which demonstrates that growth-stimulating hormone is produced at the tip of the coleoptile?

Went’s experiment was done by Frits warm out. This experiment demonstrates the growth-stimulating hormone Auxin is produced at the tip of the coleoptile.

He did a series of experiments in Avena Coleoptiles. In his first experiment, he removed the tips of Avena coleoptiles. The cut tips did not grow, indicating that the tips produced something essential for growth.
In his second experiment, he placed the agar blocks on the decapitated coleoptile tips. The coleoptile tips did not show any response.

In his third experiment, he placed the detached coleoptile tips on agar blocks. After an hour, the tips were discarded and placed this agar block on the decapitated coleoptile. It grew straight up, indicating that some chemical had diffused from the cut coleoptile tips into the agar block, which stimulated the growth.

From these experiments, Went concluded that, the chemical diffusing from the tip of coleoptile was responsible for the growth and he named it as “Auxin”.

3. Write the physiological effects of gibberellins.

1.      Application of gibberellins on plants stimulate extraordinary elongation of intemode. Eg: Com and Pea.

  1. Treatment of rosette plants with gibberellin induces sudden shoot elongation followed by flowering. This is called bolting.
  2. Gibberellins promote the production of male flowers in monoecious plants (Cucurbits).
  3. Gibberellins break dormancy of potato tubers.
  4. Gibberellins are efficient than. auxins in inducing the formation of seedless fruit – Parthenocarpic fruits (Development of fruits without fertilization) Eg: Tomato.

4. Where are estrogens produced? What is the role of estrogens in the human body?

Estrogen, the female sex hormone is produced by the Graafian follicles of the ovary.
Role of estrogen:

  • It brings about the changes that occur during puberty.
  • It initiates the process of oogenesis.
  • It stimulates the maturation of ovarian follicles in the ovary.
  • It promotes the development of secondary sexual characters (breast development and high pitched voice, etc).

5. What are the conditions which occur due to lack of ADH and insulin? How are the conditions different from one another?

ADH:
Deficiency of ADH causes a disorder called diabetes insipidus.
Deficiency of ADH reduces the reabsorption of water and causes an increase in urea output (polyuria). This deficiency disorder is called Diabetes insipidus.

IX. Higher Order Thinking Skills (HOTS) Questions

1. What would be expected to happen if,

  1. Gibberellin is applied to rice seedlings?
  2. A rotten fruit gets mixed with unripe fruits.
  3. When cytokinin is not added to the culture medium.

Answer:

  1. When gibberellins are applied, it stimulates, the extraordinary elongation of internodes.
  2. The mass of undifferentiated cell is called callus. If the rotten fruits get mixed with unripe fruits, then the ethylene produced from the rotten fruits will hasten the ripening of the unripe fruits.
  3. If cytokinin is not added to the culture medium, then the cell division, growth and differentiation will not be observed.

2. A plant hormone was first discovered in Japan when rice plants were suffering from Bakanae disease caused by Gibberella fujikoroi. Based on this information answer the following questions:
(a) Identify the hormone involved in this process.

Gibberellin is involved in this process.

(b) Which property of this hormone causes the disease?
Answer:
It stimulates extraordinary elongation of intemode.

(c) Give two functions of this hormone.
Answer:

  1. Gibberellin break dormancy of potato tubers.
  2. Gibberellin promotes the production of male flower in monoecious plant (Cucurbits).

3.Senthil has high blood pressure, protruded eyeball and increased body temperature. Name the endocrine gland involved and hormone secretion responsible for this condition.

The endocrine gland is Thyroid gland, and the hormones secreted are Triiodothyronine (T3) and Tetraiodothyronine or Thyroxine (T4). The excess secretion of the Thyroid hormone leads to Grave’s disease. The symptoms are protrusion of eyeballs (exophthalmia), increased metabolic rate, high body temperature, profuse sweating, loss of body weight and nervousness.

4. Sanjay is sitting in the exam hall. Before the start of the exam, he sweats a lot, with increased rate of heart beat. Why does this condition occur?

It is due to secretion of Epinephrine and Norepinephrine as it produced during conditions of stress and emotion. They are called as “Emergency hormones” or flight, fright and fight hormone.

5. Susan’s father feels very tired and frequently urinates. After clinical diagnosis, he was advised to take an injection daily to maintain his blood glucose level. What would be the possible cause for this? Suggest preventive measures.

The deficiency of insulin causes Diabetes mellitus. He has Diabetes mellitus. Increase in blood sugar level (Hyperglycemia). He was advised to take an injection, Insulin, which helps in the conversion of glucose into glycogen, which is stored in the liver. It decreases the concentration of glucose in the blood.
Preventive measures:

  • Manage the weight
  • Exercise regularly
  • Eat a balanced healthy diet
  • Limit alcohol intake
  • Quit smoking
  • Control the blood pressure